Honey Adulterated with Glucose Syrup: Rheological Modeling

Honey's reputation for its various both nutritional and medicinal benefits and pleasant taste ensures a sustained high demand for the product all over the world. However, honey supply is quite limited and seldom meets the demand, and consequently the product commands a relatively high price and is exposed to adulteration and imitation. Honey was adulterated with glucose syrup weight of 10%, 50%, 70% and 90%, and each sample was analysed. Pure honey at ambient temperatures exhibits peculiar non-Newtonian rheological behaviour. Adulteration with glucose syrup (a Newtonian fluid) drags its viscosity towards Newtonian flow behaviour. Malcolm Cross and Ostwald-de Waele Power-Law models were used to fit the rheological data, and the former fitted better than the latter. The behaviour indices in both models increased with increasing adulteration of honey with glucose syrup. Chromatographic characterizations of honey which provides an acceptable measure of honey quality corroborated the conclusions derived from the rheological characterization of this study.

The role of viscoelasticity in long-time cell rearrangement

Although collective cell migration (CCM) is a highly coordinated and ordered migratory mode, perturbations in the form of mechanical waves appear even in 2D. These perturbations caused by the viscoelastic nature of cell rearrangement are involved in various biological processes, such as embryogenesis, wound healing and cancer invasion. The mechanical waves, as a product of the active turbulence occurred at low Reynolds number, represent an oscillatory change in cell velocity and the relevant rheological parameters. The velocity oscillations, in the form of forward and backward flows, are driven by: viscoelastic force, surface tension force, and traction force. The viscoelastic force represents a consequence of inhomogeneous distribution of cell residual stress accumulated during CCM. This cause-consequence relation is considered on a model system such as the cell monolayer free expansion. The collision of forward and backward flows causes an increase in cell packing density which has a feedback impact on the tissue viscoelasticity and on that base influences the tissue stiffness. The evidence of how the tissue stiffness is changed near the cell jamming is conflicting. To fill this gap, we discussed the density driven change in the tissue viscoelasticity by accounting for the cell pseudo-phase transition from active (contractile) to passive (non-contractile) state appeared near cell jamming in the rheological modeling consideration.

Unveiling ductile deformation during fast exhumation of a granitic pluton in a transfer zone

<p>Exhumation and cooling of upper crustal plutons is generally assumed to develop in the brittle domain, thus determining an abrupt passage from crystallization to faulting. To challenge this general statement, we have applied an integrated approach involving meso- and micro-structural studies, thermochronology, geochronology and rheological modeling. We have analyzed the Miocene syn-tectonic Porto Azzurro pluton on Elba (Tuscan archipelago – Italy), emplaced in an extensional setting, and have realized that its fast exhumation is accompanied by localized ductile shear zones, developing along dykes and veins, later affected by brittle deformation. This is unequivocally highlighted by field studies and the analysis of microstructures with EBSD. In order to constrain the emplacement and exhumation rate of the Porto Azzurro pluton we performed U-Pb zircon dating and (U+Th)/He apatite thermochronology. It results in a magma emplacement age of 6.4 ± 0.4 Ma and an exhumation rate of 3.4 to 3.9 mm/yr. By thermo-rheological modeling we were able to establish that localized ductile deformation occurred at two different time steps: within felsic dykes when the pluton first entered into the brittle field at 380 kyr, and along quartz-rich hydrothermal veins at c. 550 kyr after pluton emplacement. Hence, the major conclusion of our data is that ductile deformation can affect a granitic intrusion even when it is entered into the brittle domain in a fast exhuming extensional regime.</p>

The Main Ethiopian Rift: Ongoing deformation inferred from earthquake mechanism

<div>The northern Main Ethiopian Rift (MER), which forms the northern part of the East African Rift System, offers an excellent tectonic setting to study the transition from continental to oceanic crust and also from tectonic to magmatic rifting. Opening of the rift started at 11 Myr ago. Until about 7 Ma, deformation was mainly accommodated at the rift border faults. Between 7 and 3 Ma, deformation migrated from the border faults to 20-30 km wide, 60 km long  magmatic segments. Earlier geodetic and field geological observations suggest that more than 80% of the present day opening of the rift is accommodated beneath these magmatic segments. On the contrary, recent observations indicate that deformation is more widespread than previously thought, with only 40% of the present day deformation being accommodated at the rift centre. </div><div> </div><div>Detailed understanding on the depth and epicentral distribution of earthquakes provides an important constraint on how strain is partitioned between the rift floor and border faults. Here I use high resolution earthquake catalogue and thermo-rheological modeling to constrain the active deformation patterns in the northern MER by assuming that the long term properties of the lithosphere represent the short term earthquake cycle. The final result of this study has significant implications for the location and magnitude of seismic hazard in the rift. </div>

Rheological modeling of pasta dough flow processes in channels of convergent-divergent inserts of molding matrix

One of efficient directions for pasta press designs modernization is installation of special conical-and-cylindrical inserts in the matrix wells in front of the dies having, like Venturi tubes, narrowing zones (convergent), expansion (divergent) and a cylindrical path located between them. However, rheological aspects of such method of forming tool modernizing in relation to pasta presses have not been studied, recommendations for structural elements calculation and design have not been developed. All this is a significant obstacle for using the method in engineering and industrial practice. The research purpose is to develop rheological models the pasta dough flow in the conical-cylindrical channels of convergent-divergent inserts and to evaluate with their help the impact of structural dimensions and rheological properties on resistance to pasta dough flow. Pasta dough was considered as a rheological complex nonlinearly viscous plastic material. In technical calculations contribution of shear strength was neglected and a rheological analysis was performed using the Oswald-de-Vila power law equation. Analytical dependences obtained make it possible to calculate the pressure drops in the convergent-divergent insert and its elements. Numerical modeling was performed and calculated data were obtained regarding the impact of dimensions of structural elements of the insert and rheological parameters of pasta dough on its resistance to viscous flow. The results obtained can form the basis of engineering and technological calculations in design of convergent-divergent inserts for laboratory and industrial matrices of pasta presses.

RHEOLOGICAL MODELING OF THE STRESS-STRAIN STATE IN FLAT COMPACTION OF COMPOSITE MATERIALS

Statement of the problem. The article investigates the deformation behavior of a composite material in the process of its flat pressing. To solve this problem, a rheological model is proposed, which is based on the phenomena occurring in a viscous (Newtonian) incompressible fluid, which occupies the volume between two absolutely rigid parallel planes of finite dimensions of rectangular shape approaching at a low speed. Within the framework of mechanics of a continuous medium under conditions of a plane deformed state, the problem is solved in two dimensions about a slow flow in the absence of volume forces and inertial effects. In this case, the solution of the equation of motion with continuity conditions is reduced to the well-known Laplace equation. In addition, on the basis of the model of linear viscoelasticity and uniaxial stress state, an attempt has been made to describe the relaxation phenomena occurring in the solidifying composite at the end of the active pressing process. Results and Conclusions. Analytical dependences of the power parameters of the stress-strain state of the compressed composite are obtained; relations for the kinematic characteristics of the pressing process are obtained; an expression is obtained for the relaxation of stresses during the technological holding of the material under pressure after the end of active pressing. The results of the study make it possible to experimentally determine the numerical values of the dynamic coefficient of viscosity and stress relaxation time, which are important characteristics in controlling the pressing processes.